Lithium ion batteries have a higher energy density and a higher power density than lead batteries and nickel-hydrogen batteries and are used in a variety of uses such as small-sized electronic devices such as smartphones, domestic backup power supply, and electric tools. In addition, attempts are underway to put high-capacity lithium ion batteries into practical use for recyclable energy storage such as photovoltaic power generation and wind power generation.
Lithium ion batteries include a cathode, an anode, an electrolytic solution, and a separator. As an electrode material that constitutes the cathode, electrode active materials made of a lithium-containing metal oxide having properties capable of reversibly intercalating and deintercalating lithium ions such as lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), and lithium iron phosphate (LiFePO4) are used, and studies are underway in order for improvement from a variety of viewpoints of an increase in the capacity of batteries, the extension of service lives, improvement of safety, cost reduction, and the like (for example, Patent Document 1).